How Do Online Auction Sites Like Ebay Attempt to Overcome

How do online auction sites like Ebay attempt to overcome the asymmetric information problems associated with goods that the buyer cannot personally inspect before purchase?

A) The online auction firm only allows high-quality merchandise to be sold at their site.
B) The previous performance (reputations) of the buyer and seller are posted for public review.
C) Buyers can take receipt of any goods before they have to pay the seller.
D) all of the above